1. Field of the Invention
The present invention relates generally to location systems for providing information services to clients as to the location of mobile user equipment (UE) terminals according to the 3GPP (Third Generation Partnership Program) Technical Specification 23.271 v. 5.3.0, “Functional stage 2 description of LCS”, pages 33-62, June 2002. More specifically, the present invention is concerned with the reuse of last known location information.
2. Description of the Related Art
The location information of a mobile UE terminal is usually sensitive to the privacy of the mobile user and often crucial when the user is in a critical situation. To protect mobile users from illegal access to their private location information, the mobile communications network is provided with a sophisticated privacy protection mechanism which imposes various restrictions on location requests according to privacy profiles (time and place) specified by the mobile users. The privacy protection mechanism provides two types of verification on a location request according to decision capability that varies with a point in the network where the location request is being served. The first type of verification is performed on a client terminal when the network receives a location request from this terminal, known as client check. The second type of verification is a permission granted to the location request after location information of a UE terminal has been obtained if the place and time interval specified by the privacy profile of the UE terminal user are satisfied, known as privacy check.
Mobile network providers, on the other hand, are required to provide location service in addition to their basic mobile communications service. Specifically, the location service involves several network nodes exchanging special messages with one another for the position calculation of a target UE and exchanging messages with a target UE terminal over wireless link.
The 3GPP location information system, as specified in the 3GPP standard, is basically made up of client terminal, GMLC (Gateway Mobile Location Center), SGSN/MSC (Serving General packet radio service Support Node/Mobile Services switching Center), local wireless network known as RAN (Radio Access Network) and UE (User Equipment) terminal connected to the RAN via wireless link. HLR/HSS (Home Location Register/Home Subscriber Server) is connected to the GMLC as a database for holding the identity of the RAN to which UE terminals are connected. Registered client terminals are given exclusive right to access UE terminals.
The 3GPP standard provides two modes of operation for requesting location information, i.e., the mobile terminated location request (MT-LR) and the mobile originated location request (MO-LR). In the MT-LR mode, the client terminal can either request the current location of a target UE or the current or last known location of this terminal. The last known location information is used as a location report instead of the current location information when the network has failed in locating the target UE for some reason if the last known location information is usable.
More specifically, when the network receives a location request for a target UE, the SGSN/MSC responsible for the management of the target UE is also responsible for the privacy protection of the UE terminal. According to the privacy protection of the MT-LR mode as specified by the 3GPP standard, UE mobile users register their privacy profile (e.g., the identifiers of those clients allowed to request their location) in the SGSN/MSC of their home network. In response to a location request, the SGSN/MSC performs a privacy check by verifying it against the registered privacy profile of the target UE and determines whether or not the location request is granted. If the privacy profile of a UE terminal further specifies that a notification/verification request be sent to the UE terminal, the UE terminal is given a notification that it is being targeted or verifies the location request and returns a verification result to the client terminal. When the location request is acceptable, the SGSN/MSC proceeds with a location estimation process in collaboration with the associated RAN to determine the current location of the target UE. If the SGSN/MSC fails to acquire current location information of a target UE, a copy of the stored last known location information of the target UE is transmitted to the client terminal if this information is currently still usable, or significant.
In the MO-LR mode, the mobile UE terminal exclusively requests its own current location from the network. In this mode, a failure in location measurement will result in the transmission of an error report to the requesting mobile UE terminal. Last known location information is not reused at all for transmission instead of the error report.
However, a number of shortcomings exist in the prior art location system.
First, the flow of traffic through the location network and the amount of location measurement calculations increase in proportion to location requests from client and mobile terminals. Further, part of the location network is shared in common by a mobile communication network. Therefore, when the location network experiences heavy traffic loads, it is likely that mobile communication traffic is adversely affected, which could lead to an extra burden on mobile network providers.
Second, in the MT-LR mode of operation, privacy check is performed by the SGSN/MSC. If reusable last known location information of a UE terminal is available in the GMLC, for example, the SGSN/MSC would perform privacy check for the UE terminal. However, no mechanism is provided for the GMLC to request the SGSN/MSC to perform privacy check. As a result, privacy protection of last known location information is only ensured when this private information is maintained in the GMLC.
Third, the reusability of last known location information depends exclusively on whether or not an SGSN/MSC is holding the last known location information, and the criteria of usability depends on specific details of an SGSN/MSC which may differ among different SGSN/MSCs. Therefore, it is likely that requesting client terminals may receive worthless last known location information.